Re: OK to use TV coax for microphone?

On Sat, 03 May 2008 21:23:08 -0400, "Michael A. Terrell"
<mike.terrell@[EMAIL PROTECTED]
> wrote:

>   Then you've never seen the wire used by cable TV and Satellite TV
>companies. Pure copper is too expensive these days, and too soft for
>repeated flexing.  If you want to pay over a dollar a foot for copper
>core TV coax, go ahead. The last time I had to buy some it was about
>eight times the price of the foil ****eld W/braid TV coax, and useless
>for UHF.  Use a magnet, and see for yourself. The copper plating smears
>when cut with dykes, and makes the coated steel appear to be solid
>copper.

Well, I did just that.  I grabbed a magnet off the fridge and went
through my pile of RG-6/u CATV coax jumpers and cables.  The really
old stuff had an all copper center conductor.  The fairly current
stuff has a copperweld or CCS (copper clad steel) center conductor.  I
would guess that about 90% of what's in the pile (about 100 cables) is
CCS.  Amazing:
<http://www.fu****international.com/Products.aspx?p=Bimetallic>
<http://www.fu****international.com/Products.aspx?p=CCSCable
>

However, much of the RG-6/u cable is "satellite grade", which means it
should work to about 2GHz with minimal loss.  I've been using the quad
****elded variety (apparently with a CCS center conductor) for years
for Wi-Fi at 2.4GHz with about 10dB/100ft attenuation (measured).  The
loss is in the dielectric, not in the center conductor cladding.  I
would say that it works just fine at UHF (300-3000MHz).

Incidentally, I blundered across this data sheet for RG-6/u.  They can
make it just about any way you want it, and still call it RG-6/u. Note
the line with:
  6) Braiding coverage: Between 30 - 97% available; 
I can't imagine who would want to buy 30% coverage outer ****elding.
<http://www.tootoo.com/supplier/product-detail/6251149/RG6%252fU.html>

As for the coax being brittle, that's possible if it were plenum rated
cable for running through air ducts.  The stuff is suppose to be "low
smoke" when burning.  It tends to be rather stiff and brittle.  For
RG-6/u, the flexibility is largely in the type of braid and outer
jacket.  Quad ****elded is going to be rather stiff.  Judging by the
mixture in my junk box, I have cables that range from super flexible
(for the back of HDTV installs) to super stiff (gel filled for direct
burial).  Your mileage and stiffness may vary.

As for the suitability as a microphone cable, I dunno.  The original
posting had no useful descriptions of the microphone, the found cable,
or the equipment to which it will be connected.  4.8mm O.D. could be a
wide variety of possible coax cables.  I'm lazy and don't wanna guess.


-- 
Jeff Liebermann     jeffl@[EMAIL PROTECTED]
 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558